SBI3U1 Unit 5: Animals

Metabolism

Chemical processes of the body’s cells to convert food into usable energy.

Metabolic rate

The rate at which the body converts stored energy to working energy

Basal metabolic rate

The metabolic rate when the body is at rest

Gastrovascular cavity

One opening through which food is eaten and waste is expelled

Complete digestive system

Has 2 openings, one for food intake and one for waste elimination

Gastrointestinal tract description

Passageway extending from mouth to anus, 7-9m in length and technically considered to be outside of the body

Functions of the digestive system

Begins metabolism by breaking down food into nutrients, absorbs the nutrients into the circulatory system

Six main nutrients

Carbs, proteins, lipids, vitamins, minerals, water

Stages of digestion

Ingestion, digestion, absorption, egestion

Ingestion stage

Consuming food

Digestion stage

Breaking down food into nutrients

Absorption stage

Moving nutrients into cells, then the bloodstream

Egestion stage

Removing leftover waste

Organs of the gastrointestinal tract

Mouth, pharynx, esophagus, stomach, small intestine, large intestine (colon), rectum, anus

Digestive system accessory organs/structures

Teeth, tongue, salivary glands, epiglottis, uvula, gut bacteria, liver, gallbladder, pancreas, appendix, mesentery

Teeth function

Grind food into smaller pieces

Salivary glands function

Secrete fluid to lubricate food and amylase enzyme to begin chemical digestion of starch

Uvula function

Dangling fleshy ball that secretes saliva and prevents liquid going up the nose when swallowing

Tongue function

Moves chewed food around to form a ball called a bolus

Pharynx function

Guides food and liquid to esophagus

Epiglottis function

Covers the trachea during swallowing to make sure the food goes to the esophagus

Peristalsis

Wave of involuntary muscular contractions that push the bolus down to the stomach

Esophageal sphincter function

A sphincter that keeps stomach acid outside of the esophagus

Esophagus function

Transports foods/liquids from the mouth to the stomach

Stomach function

A folded muscular sac that performs physical and chemical digestion. Muscles contract, resulting in churning, a form of physical digestion.

Pepsin function

An enzyme that chemically digests proteins

Stomach acid function

Kills of harmful viruses/bacteria and aids in chemical digestion

Mucus in stomach function

Protects the stomach lining from its acid

Chyme

Partially digested food which leaves the stomach by passing through the pyloric sphincter

Substances absorbed in the stomach

Medicines like aspirin, alcohol, and water

Small intestine function

Where most of nutrient absorption occurs

How the liver and pancreas support digestion

They produce and secrete enzymes into the small intestine

Parts of the small intestine

Duodenum, ileum, jejunum

Duodenum function

Mainly chemical digestion. Enzymes and bile produced in the liver and pancreas are secreted into this organ

Bile function

Produced in the liver and stored in the gallbladder, it emulsifies fats to increase surface area for digestion

Pancreas function

Secretes juices containing lipases to break down fat, lactase and amylase to break down carbs, and proteases like trypsin to break down proteins

Jejunum function

Main function is nutrient absorption. It is lined with villi which increase surface area for nutrient absorption

Villi

Finger-like projections covered with microvilli to increase the surface area for nutrient absorption

Ileum function

Main function is to finish nutrient absorption and absorb what the jejunum didn’t absorb

Appendix function

Likely provides a safe harbour of good bacteria during gastrointestinal stress

Large intestine function

To absorb water from what is left after digestion. Most gut bacteria is here and it supports digestion by producing vitamins B and K and breaking down fibre/cellulose

Rectum function

Storage for leftover waste

Mesentery

A folded membrane that suspends stomach and intestines to the abdominal cavity, supplies the intestine with blood vessels, and supplies the intestine with nerve and lymph vessels

Factors that influence gut flora in infants

Vaginal/c section birth, method of feeding, breastfeeder’s diet, geographical location, interactions with people and animals

Prebiotics

Foods that contain substances that humans can’t digest, like fibre, but are a food source for gut bacteria

Probiotics

Foods where living bacteria are found which can help form a healthy gut microbiome

Benefits of a healthy gut

Immune health, heart health, lower risk of diabetes and allergies, mental health and skin health

Gut-brain connection

The mesentery provides an extensive nervous network with more than 100 million nerve cells to the GI tract. This is called the enteric nervous system

IBS

Irritation to GI system which sends signals to the central nervous system and triggers mood changes

Lactose breaks down to

Glucose and galactose which are smaller monosaccharides that can easily be absorbed into the bloodstream

Lactase

Enzyme that breaks down lactose

Evolution and lactose intolerance

Humans with ancestors who domesticated milk-producing animals are more likely to keep the lactase-producing gene on later in life

Celiac disease

Autoimmune disorder where undigested short fragments of gluten (specifically gliadin) can build up in small intestine cells, and the gliadin sends signals to the immune system that something is wrong. Macrophages attack the enterocytes and eventually destroy the villi, reducing the body’s ability to absorb nutrients

Processes of respiration

Breathing/ventilation (external respiration), gas exchange (internal respiration), cellular respiration

Respiratory system functions

To provide red blood cells with oxygen that the body’s tissues need, to remove carbon dioxide waste from red blood cells produced by tissues,

Mouth and nasal cavities functions

Air enters through the 2 nasal cavities or the mouth, nasal cavities warm and moisten air and are lined with mucus and hair that filter air and trap dust

Pharynx (respiratory system) structure

Nasal cavities lead to the pharynx which branches into 2 openings, trachea (windpipe) and esophagus (digestion)

Larynx structure

At the top of the pharynx, air passes through the larynx, a cartilaginous structure that prevents food from entering the lungs and also contains the vocal chords

Trachea/bronchi structure

Supported by rings of cartilage, preventing them from collapsing so air can flow freely

Epithelial cells

Line the trachea and bronchi, producing mucus and have cilia, which move mucus and filter out foreign material that enters the lungs

Alveoli structure

Tiny sacs that make up the majority of lung tissue, surrounded by capillaries

Alveoli function

Increases surface area for gas exchange, have a thin membrane to facilitate diffusion of gases, have a good blood supply from capillaries

Gas exchange definition

Once air is in the lungs, oxygen diffuses across the cell membrane of the alveoli into a web of capillaries surrounding each alveolus

Gas exchange: Diffusion

Oxygen enters rbcs and binds to hemoglobin, carbon dioxide moves from the red blood cells into the alveolus

Diffusion

A passive process where molecules move from an area of high to low concentration

Lung capacity vs average breath

An average adult has a lung capacity of 5-6L, but a resting breath is only 0.5L and we only extract 25% of the available oxygen in the air we inhale

Diaphragm structure

The major muscle of ventilation, which is a large dome shaped muscle just under the lungs

Intercostal muscles function

Involved in opening and closing the ribcage, usually acting involuntarily

Inhalation: muscle contraction

Intercostal muscles contract, pulling the ribs outward and up, and diaphragm contracts, pulling lungs downwards, leading to an increase in lung volume

Inhalation: diffusion

The increase in lung volume leads to reduced concentration in the alveoli, and air moves from high to low concentration so air moves from the external environment into the lungs

Exhalation: muscles

Intercostal muscles relax and allow the lungs to return to their initial position, and the diaphragm relaxes, allowing lungs to move back upwards, leading to a decrease in lung volume

Exhalation: Diffusion

Reduction in lung volume leads to an increase in air concentration in alveoli, so air moves from lungs into the external environment

Pleural membrane

Surrounds the lungs and cushions and protects them, releases a small amount of liquid into the pleural space which prevents friction between the lungs and chest cavity

Factors affecting ventilation

Breathing rate, total lung capacity, tidal volume, vital capacity, residual volume

Breathing rate

Number of breaths taken per minute, average human resting rate is 12-20, however it changes based on different conditions

Factors that affect breathing rate

Physical activity, age, altitude, emotional state, temperature

Total lung capacity

Volume of air in the lungs after a maximum effort inhalation

Tidal volume

Amount of air that moves in and out of the lungs each respiratory cycle

Vital capacity

Greatest amount of air that can be expelled from the lungs after a maximum inhalation

Residual volume

Amount of air remaining in the lungs after a maximum effort exhalation

Pneumothorax

Collapse of a lung when air escapes the lungs and enters the pleural space, most commonly in young, tall, thin males due to rapid growth spurts putting increased pressure on the lungs

Pneumothorax treatment

A chest tube to remove excess air, or surgery

Pneumonia

Any infection of the lungs caused by bacteria, virus, or fungi, often beginning as bronchitis and moving into the lungs. Results in inflammation and buildup of fluid in the alveoli, resulting in difficulty breathing

Pleural effusion

Occurs when fluid builds up in the pleural space which impacts lung function. Causes can include pneumonia, cancer, or complications from heart/lung/kidney disease

Pleural effusion treatment

Thoracentesis, which involves placing a hollow needle using ultrasound to drain the fluid

Asthma

Chronic condition which results in narrowing of the bronchi and bronchioles and possible production of mucus. It results in difficulty breathing and possibly coughing/wheezing

Asthma treatment

Inhalers, which deliver medication to dilate the airway

Circulatory system functions

Deliver oxygen from lungs to cells, deliver carbon dioxide from cells to lungs, regulate body temperature, transport disease-fighting white blood cells to location of invaders, transport hormones to send signals to the body

Red blood cells structure

Make up about 45% of blood by volume, do not contain a nucleus, and hemoglobin makes them red

Erythrocytes

Red blood cells

Hemoglobin structure

A protein molecule made of 4 chains. Each rbc has 270 million hemoglobin molecules and each hemoglobin molecule contains 4 iron atoms which bind to the oxygen

Production of red blood cells

2 million rbcs are produced each second, but since they lack nuclei they don’t divide, they are produced from stem cells in bone marrow and typically live 120 days before being destroyed in the spleen and liver

Red blood cell shape

They are disk shaped with a flattened centre, allowing them more surface area of oxygen binding to hemoglobin, provides flexibility as cells move through narrow vessels

White blood cell function

Infection-fighting cells in the blood which recognize and destroy invaders. They make up less than 1% of blood by volume and are the only blood cells with a nucleus and which function outside of blood vessels

Platelets function

Tiny blood cells that facilitate blood clotting by spreading across damaged blood cells and breaking apart to release clotting agents and grow sticky tentacle-like projections out of a protein called fibrin

Scab formation

Fibrin tentacles attach to other platelets and trap rbcs and send out chemical signals for more platelets to come to the damage site and eventually form a clot and scab

Plasma function

A protein-rich fluid that carries blood cells along as well as nutrients, waste, proteins, electrolytes, and water. They make up more than 50% of blood by volume

Arteries function

Carry blood away from the heart, meaning blood in the arteries is under the most pressure, so artery walls are thick to withstand the pressure

Artery structure

Thick-walled vessels lined with smooth muscle which can contract or dilate to change the width of these vessels

Veins function

Carry blood towards the heart and have valves to prevent backflow. They are lined with smooth muscle that can contract or dilate to change the width of the vessel